Monoclonal antibodies (mAb) are used to treat a variety of cancers and other diseases. Dosing is typically based on body surface area, but population pharmacokinetic (PK) data suggests considerable variation across patients. Furthermore, there is growing evidence that patients with low final trough levels of circulating antibody have a poorer outcome, suggesting that dynamic monitoring of blood antibody levels and treating until a defined threshold is obtained may improve outcomes. Similar pharmacokinetic dosing has greatly improved some chemotherapy agents. We have previously developed laboratory assays for the quantitation of mAb in treated patients and lateral flow immunoassays (LFA) for counterfeit detection using mimetope peptides that specifically bind to a given mAb. For this project, we propose to develop prototype LFA devices that can determine if a given mAb is present in a blood sample above a predefined threshold concentration (CT). Devices will be produced and benchmarked for the three most commonly used mAb: trastuzumab, bevacizumab, and rituximab. The latter will validate on samples from treated patients. Our devices leverage the generalized nature of mimetope peptides as an immunoassay reagent as well as the simplicity and convenience of lateral flow to create a line of products that can be standardized across therapies.